A. Field of Invention
The present invention is related to wireless communication systems, and more particularly, to a method and system of increasing the forward channel capacity in a CDMA communication network. It is particularly useful for providing high rate data communications to a plurality of users.
B. Description of Related Art
In a typical wireless communication system, an area is divided geographically into a number of cell sites, each defined by one or more radiation patterns created by an emission of radio frequency (RF) electromagnetic (EM) waves from a respective base transceiver station (BTS) antenna. Each cell site is typically further divided into two, three, or more sectors, where the sectors provide radio coverage for a selected area within the cell site. Each sector of the cell typically uses dedicated antennas to provide the required coverage.
Changes in the CDMA specifications set forth in CDMA2000 increased capacity in the forward and reverse channels. In particular, the SNR requirements for each channel (forward and reverse) have been improved. The IS 2000 specification doubled Walsh code space over IS95 to provide 128 Walsh codes, thereby doubling the forward channel capacity.
CDMA networks have been improved to provide data services, referred to as 1xEVDO (Evolution, Data Only). In 1xEVDO, an entire carrier (1.25 MHz modulated bandwidth) is dedicated to high-speed packet data, while one or more additional carriers are used in the normal manner for voice. In such a system, all of the forward link resources are used to send data to a single user for a given time period, or time slot. In other time slots, the channel is used to provide data bursts to additional users. More specifically, 1xEVDO operates in the forward link by segregating the forward link into time slices of 26.67 ms. For the period of the 26.67 ms, a single user is given all of the RF resources in order to deliver packet data information to an end terminal requesting data.
As a further evolution of CDMA technology, CDMA2000 1xEV-DV (Evolution Data/Voice, see CDMA2000 Release C or Release D) and 1xEV-DO (Evolution Data Only Release A) provides integrated voice with simultaneous high-speed packet data services at speeds of up to 3.09 Mbps. The 1xEVDV standard provides packet data and voice in the same carrier, but retains the ability to maintain packet services on a separate carrier if desired. 1xEVDO-A while still focused on data optimization, provides quality of service mechanisms to enable voice over Internet Protocol (IP).
Even with the evolution to faster data rates, there exists a need to provide still further improvements to increase the capacity and data rates to wireless users. Consequently, a CDMA communication system that allows additional users that overcomes the current limitations is needed.